Circadian clock in cancer cells participates in the hallmarks of cancer, including replicative immortality, proliferative signaling maintenance, invasion and metastasis activation, cell death resistance, and energy metabolism reconfiguration.19 To explore the circadian characteristics of human OSCC, we first assayed the circadian rhythm of OSCC by examining the expression pattern of clock genes in xenografts from OSCC cells. This evidence concerns the gene CLOCK and cancer.